Relay circuit



8, 1950 R. G. RQWE EI'AL 2,518,380

RELAY CIRCUIT Filed April 19, 1945 MIN. CONTROL MA X.

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VOLTAGE ATTORNEYS Patented Aug. 8, 1950 UNITED STATES PATENT OFFICERELAY CIRCUIT Application April 19, 1945, Serial No. 589,152

I 10 Claims. Our inventionrelates to relay circuits and, moreparticularly, to such circuits using gaseous conductor or thyratrontubes for controlling the energization of a load device or circuit.

As is well known to those versed in the art, gaseous conductor orthyratron tubes'contain essential cathode, grid and anode elementsusually in a low pressure atmosphere of mercury vapor, neon, argon andsimilar gases or combinations thereof. By proper manipulation ofelectrode potentials and circuit parameters the gas in a given thyratroncan be ionized. When the contained gas is ionized the anode-cathodecircuit is substantially conducting and the tube is said to be fired.When the contained gas is not ionized the anode-cathode circuit issubstantially non-conducting and the tube is said to be extinguished.For convenience, the process or state of being fired can be termedignition"; the process or state of being extinguished can be termedextinction.

For a thyratron of given characteristics, ignition and extinction may becontrolled by the direct current grid voltage for certain combinationsof cathode and anode potentials.

However, if direct current is used for the anode supply, the grid losescontrol after the tube has once fired and it becomes necessary to breakthe anode supply circuit to extinguish the tube. In

order to permit the grid to retain control over the anode current andextinguish the tube it is common practice to employ alternating currentfor the anode supply, which eiiectively reduces the anode voltage tozero once during each supply voltage cycle. --Being conductive on onlyalternate halves of the supply voltage cycle, the tube fires andextinguishes at a rate equal to the supply frequency, and the grid canregain control during periods of extinction.

With circuit parameters adjusted for normal operating conditions withthe tube in the extinguished state, the grid-cathode potential whichwill just fire the tube may be called the ritical ignition potential.With theftube in the fired state, the grid-cathode potential which willjust extinguish the tube may be called the critical extinctionpotential.

Many relay circuits employing thyratrons, both of the gas-triode andgas-tetrode types have been proposed for the switching of heavy-duty,high powered electrical load circuit: by exceedingly small controlvoltage changes. Some thyratron tubes, in particular those of thehot-cathode gas-tetrode type in typical circuit connections, can befired and extinguished by as little as 0.05 volt change in control gridbias at exceedingly minute currents. Thus, a power relay or othercurrent responsive electrical load device coupled in the thyratronanode-cathode circuit can be controlled by very small grid bias voltagechanges at very low power requirements.

We have found, in fact, that such circuits are often too sensitive tosmall changes in control grid voltage, In systems in which the controlgrid bias voltage slowly approaches the critical" ignition or extinctionpotential, operation of the circuit becomes erratic, unstable andunreliable.

A. further fault in prior art thyratron tube relay circuits is thatwhile they have eliminated some of the disadvantages they have notretained the advantages of the easily controlled sensitivity and theadjustable "pick-up and dropout features of the magneto-mechanicalelectric relay.

One object of our invention is to provide a thyratron tube relay circuitwith improved sta bility, reliability, and resistance to chatter andmisfire.

Another object of our invention is to provide a thyratron tube relaycircuit with easily variable sensitivity.

A further object of our invention is to provide a simple thyratron tuberelay circuit wherein the applied control potential required to fire thetube may be substantially diiferent from that required to extinguish thetube and wherein the difierence in these two potentials is easily,cheaply. and readily controllable.

The novel features which we believe to be characteristic of ourinvention are engendered with particularity in the appended claims; theinvention itself, however, will be best understood by reference to theaccompanying description and drawings, in which:

Figure 1 shows a typical thyratron tube relay circuit.

Figure 2 shows the approximate grid voltageplate current characteristiccurve of a typical thyratron tube relay circuit.

Figure 3 shows a magnetic-mechanical electric relay circuit.

Figure 4 shows the approximate pick-up and drop out characteristics of amagneto-mechanical electric relay.

Figure 5 shows a thyratron tube relay circuit employing the principlesof our invention.

Figure 6 shows the approximate grid voltageplate current characteristiccurve of a thyratron tube relay circuit employing the principles of ourinvention.

With reference to Figure 1, alternating current power supply lines I and2 supply, through transformer 3, the filament voltage to filament 4 andthe anode voltage through the field coil of relay l2 to anode 5 andcathode of thyratron tube 8. Potentiometer II and battery I0, connectedas shown to cathode 6 and grid 0, cooperate to represent any source ofvariable control voltage desired to activate the relay circuit. Such asource, represented by box I6 and terminals II and I3, might be, forexample, the voltage drop subtended across an impedance carrying currentor the like. Shield grid I of thyratron tube 8 is connected to cathode 6and is not further essential to a simple description of circuitoperation. Filter condenser I is usually essentialto prevent chatter inrelay I2 caused by the interrupted unidirectional current flow throughtube 8 on only alternate halves of the supply voltage cycle. Power relaycontacts i3 and I4 are open when tube 8 is extinguished and closed whentube 8 is fired. For a given combination of filament and anodepotentials along with other circuit parameters, the ignition and,extinction of tube 3 and thereby by the condition of relay contacts I3and I4 is determined by the applied control potential across cathode 6and grid 9.

For example, using a thyratron tube type number 2050 or a tube havingsimilar characteristics, with 6.3 volts applied to the filament and 115volts 60 cycle alternating current for the anode supply, circuitparameters can be adjusted so that the tube will fire with approximately2.05

volts and extinguish with approximately .10

vol-ts negative grid bias, a difference of 0.05 volt.

Figure 2 illustrates the operation of this circuit graphically in arough approximation. The control voltage is that supplied from controlsource :8 across terminals ii and I8. With reference to both Figures 1and 2, this control voltage is equal to the grid voltage of tube 8applied from grid 9 to cathode 6 regardless of the condition of ignitionor extinction of tube 8 because of the low impedance in the circuit. 7

In Figure 2 the solid vertical line represents the critical extinctionpotential and the dotted vertical line the critical ignition potential.In practice these two potentials do not exactly coincide, but, as shownroughly in the graph, differ by only 0.05 volt. As the applied controlvoltage is slowly varied from negative 3 volts toward zero volts, forexample, the tube will fire at .05 volts. As the applied control voltageis slowly varied from zero toward negative 3 volts, the tube willextinguish at 2.10 volts. However, using slowly varying applied controlvoltage as is often desirable and as may be produced at terminals I1 andI8 in Figure l, the tube becomes unstable when either the criticalfiring or extinguishing potentials are approached. Unreliable anderratic operation of the circuit occurs, particularly in the case ofslow-varying control voltage.

Figure 3 illustrates a typical magneto-mechanical electric relay M, withfield coil terminals 22 and 23 coupled directly to output terminals I!and I8 of control voltage source It and with secondary power contacts 24and 25 provided for coupling in the power circuit to be controlled.

Figure 4 illustrates graphically the operation of relay 2| and isprepared such that for practical purposes of interpretation the actionsof relays and relay circuits in all or the figures shown can becompared. For example, in Figure 2 the solid vertical line representsthe circuit control voltage at which thyratron tube 8 will extinguish,whereas in Figure 4 the solid vertical line represents the circuitcontrol voltage at which the armature of magneto-mechanical relay 2|will drop out. In Figure 2 the dotted vertical line represents thecircuit control voltage at which thyratron tube 3 will fire, Whereas inFigure 4 the dotted vertical line represents the circuit control voltageat which the armature of magneto-mechanical relay 2i will pick up. Thus,the pick-up and drop ou of the magneto-mechanical relay can be likenedto the ignition and extinction of thyratron tube 8, relaying beingaccomplished in each case by the ability of each device to control high-:1 power secondary loads from control voltages having low power and/ormagnitude.

Comparison of Figures 2 and 4 shows that a larger difierence in appliedcontrol voltage exists between "pick-up and drop-out ofmagnetomechanical electric relay 2| than exists between ignition andextinction of the thyratron tube relay. Further, with reference toFigure 3, the difierence between pick-up and drop-out control voltagerequirements for relay 2! may be easily controlled within wide limits bysimple adjustment of thumb-screw 26 in cooperation with tension spring21, along with thumb-screw 28 for controlling the initial spacingbetween armature contact 29 and fixed contact 30. For example, if theinitial spacing between armature con tact 29 and fixed contact 30 isincreased, the difference in control voltage between pick-up anddrop-out increases; if the initial contact spacing is decreased, thediflerence in control voltage decreases. However, in prior art thyratrontube relay circuits no such simple expedient exists for controlling thedifference between ignition and extinction control voltages.

With reference now to Figure 5, an illustration of one embodiment of ourinvention, the circuit and components are identical with those in Figure1 with the exception that we prefer to employ in addition resistor I9 inseries connection with grid 9 and control voltage source terminal H, aswell as condenser 20 in shunt with grid 0 and cathode 6 of tube 8. Byvarying the resistance of resistor I9, which may be a low-priced radiopotentiometer or the like, we have found that we can obtain acontinuously adjustable difference between the applied control voltagerequired for ignition and that required for extinction and resultsclosely comparable to those ob tained with the magneto-mechanical relay.

Using the constants and voltages as described in connection with Figure1, but with the addition of resistor I9 and condenser 20 as described inconnection with Figure 5, the following difierences between ignition andextinction control potentials as supplied from source I 6 throughterminals [1 and I8 are noted:

. Oong g denser Ignition Extinction ohms 12101,f (11151 voltage voltageNone None 2. 05 2. 10 10, 000 1. 0 2. 25 2. 60 15, 000 l. 0 2. 25 3. 4020, 000 1. 0 2. 25 3. 8O 25, 000 1. 0 2. 25 4, 60 51, 000 1.0 2. 25-7.40

Further, by following the practice of our present invention, thestability and reliability of prior art thyratron relays can be greatlyimproved. The circuit containing the disclosed modifications exhibits alocking-in characteristic, which in many applications is extremelydesirable, such that once the tube fires or extinguishes small controlvoltage changes will not disturb the present condition of the circuit.It will be appreciated that by modifications in the values of resistorl9 and condenser 28, smaller difierences between the values of ignitionvoltage and extinction voltage can be obtained, except as limited by thevalues with neither resistor l9 nor condenser 20 in the circuit.

At the instant of ignition, a voltage is developed across resistor l9,the magnitude of which is determined in part by the RC combination ofresistor is and condenser 26, for eiTecting this diiierence betweenignition and extinction control voltage, as measured across terminals l1and I8, may be accomplished by holding resistor l9 constant whilevarying the capacity of condenser 20, as shown below:

The polarity of the voltage developed across resistor 19 due to currentflow is of a sense such that the negative potential existing fromcathode 6 to grid 9 of tube 8 is eiiectively reduced; that is,approaches zero potential when tube 8 fires. This potential drop whichappears across resistor iii when tube 8 fires adds algebraically to theapplied control potential across terminals ll and I8 and therebyproduces the locking-in features characteristic of the present inventionresulting in vastly improved stability, reliability and resistance tochatter and misfire. In order for extinction of the tube, the appliedcontrol voltage at terminals i1 and [8 must increase in a negativedirection until the algebraic sum of the control voltage and the voltagedrop across resistor i9 is equal to the actual critical extinctionpotential. After extinction of thyratron tube 8, the additional voltageappearing across re sistor iii is reduced to substantially zero and thesystem is automatically and instantaneously recycled for a subsequentoperation. In the pressent circuit the grid voltage of tube 8 asmeasureol from cathode ii to grid 9 is no longer always equal to theapplied control voltage. The introduction of resistor Iii, byeffectively increasing the impedance of the control source, and theapplication of condenser 20 to efiectively store the periodic chargingvoltage during extinction cycles, permits a new voltage component to beautomatically produced when tube 8 fires and permits the thyratron relayto function in a novel and desirable manner.

Figure 6 illustrate graphically the nature of the relay characteristicsobtainable by practicing the art of the present invention. Comparisonwith Figure 4 shows how the characteristics of the magneto-mechanicalelectric relay are simulated. By simple adjustment of variable resistord, the difference between thecontrol voltage across terminals H and I8required for ignition and that required for extinction can be controlledfrom nearly zero to as large a practical value as is desirable.

While we have shown and described in detail a preferred embodiment ofour invention, we are aware that it is adaptable to rearrangement andmodification without departing from the true spirit and scope thereof.Therefore, we wish it understood that we are not necessarily limitingthis invention to the precise embodiment herein disclosed, except in sofar as we are limited by the appended claims.

We claim as our invention:

1. A method for controlling a, thyratron gas discharge device having atleast two control electrodes, comprising producing a variable controlpotential by means external to said thyratron, internally producing apotential across said control electrodes by positive ion flow duringiterative ignition periods of said thyratron, storing said last-namedpotential during intervening extinction periods of said thyratron andsimultaneously applying said externally-produced control potential andsaid internally-produced stored potential to said control electrodes.

2. A method for controlling a thyratron gas discharge device having atleast two control electrodes, comprising producing a variable controlpotential by means external to said thyratron, internally producing apotential across said control electrodes by positive ion flow duringiterative ignition periods of said thyratron, storing said last-namedpotential during intervening extinction periods of said thyratron andapplying the algebraic sum of said externally-produced control potentialand said internally-produced stored potential to said controlelectrodes.

'3. A method for controlling a thyratron gas discharge device having atleast two control elec-= trodes, comprising producing a variable controlpotential by means external to said thyratron, internally producing apotential cross said control electrodes by positive ion flow duringiterative ignition periods of said thyratron, storing said last-namedpotential during intervenin extinction periods of said thyratron andapplying said externally-produced control potential and saidinternally-produced stored potential simultaneously to said controlelectrodes, whereby a substantial difierence between the controlpotential required for ignition and that required for extinction of saidthyratron obtains.

4. A method for controlling a, thyratron gas discharge device having atleast two control electrodes, comprising producing a variable controlpotential by means external to said thyratron, internally producing apredetermined potential by positive-ion grid-current flow between saidcontrol electrodes during iterative ignition periods of said thyratron,storing a predetermined portion of said last-named potential duringinter= vening extinction periods of said thyratron and simultaneouslyapplying said externally-produced control potential and saidinternally-produced stored potential to said control electrodes, wherebya predetermined difference between the control potential required forignition and that required for extinction of said thyratron obtains.

5. In a relay circuit comprising a pulsating supply potential, 3,control potential variable by external means, a load and a gasdischargetube having at least an anode, a cathode and a grid electrode, said lasttwo elements comprising a pair of control electrodes and said supplypotential being connected through said anode and cathode to said load;means to produce a substantial difference between the contro otentialrequired for ignition and that required for extinction of said' gas tubecircuit. comprising a first connection between one side of said controlpotential and: one of said control electrodes; a second connectionincluding resistance between the other side of said control potentialand the other control electrode and a capacitance connected in shuntwith said control electrodes; said resistance means being: limited tosuflicientf resistance to produce substantial potential, pulsesthereacross by positiveeion grid-current therethrough during. eachconducting cycle of said gas tube, and said capacitance: means beinglimited to sumcient capacitance to store a substantial portion of saidion-current-producedpotential for a time corresponding to at least onehalf cycle of said pulsating supply potential frequency.

6; A method for controlling a thyratrongas discharge tube. having atleast two control electrodes, comprising producing a variable controlpotential by means external to said thyratron,

internally producing a, potential of adjustable range by positive-iongrid-current flow between said control electrodes during iterativeignition periods of said thyratron,. storing a substantial portion ofsaid last-named potential-during inter'vening extinction periods ofsaid; thyratrc-n and simultaneously applying said externallyproducedcontrol potential: and said internallyproduced stored potential to saidcontrol e1ectrodes, whereby anadjustable difference between the controlpotential required for ignition and that required for extinction of saidthyratron obtains.

'7. A method for controlling a thyratron gas discharge tube having atleast two control electrodes, comprising. producing a variable controlpotential by means external to said thyratron, internally producing apotential by positive-ion grid-current flow between said controlelectrodes during iterative ignition periods of said thyr-atron, storingan adjustable portion of said lastname'd potential during intervening.extinction periods of said thyratron and simultaneously ap-. plying saidexternally-produced control potential and said internally-producedstored potential to said control electrodes, whereby an'adjustabledifference between the control potential required for ignition and thatrequired for extinction 01" said thyratron obtains.

8. In arelay circuit comprising a pulsating supply potential, a controlpotential variable by external means, a load and a gas discharge devicehaving at least an anode, a cathode and a grid electrode, said last twoelements comprising a pair of control electrodes. and said supplypotential being connected through. said anode and cathode to saidv load;means to produce a substantial diiference between the controlpotentialreauired for ignition and that required for extinction of saidcircuit, comprising resistor means of sufficient resistance to producesubstantial po tentialpulses thereacross by positive ion grid currenttherethrough during each ignition cycle of said gas discharge device,capacitor means of sufiicient capacitance to store a substantial portionof said ion-current-produced potential for a time corresponding to atleast one half cycle of said pulsating supply potential, frequency andcircuit means arranged to connect said resistor between the controlpotential and the control electrodes to establish said ion-currentpotential and to connect said capacitor in shunt with said controlelectrodes to store said ion-current potential.

9. In a relay circuit. comprising a pulsating;

pair of control electrodes and saidsupply potential beingconnectedthrough said anode and cathode to said load; a modifyingnetwork arranged; to connect said control potential and said controlelectrodes, including resistance means having sufiicient resistance to;produce substantial potential pulses thereacross by positive ion gridcurrent therethrough, a capacitance means having sufficient capacitanceto store a substantial. portion of said ion-current-produced potentialfor a time corresponding to at least one half cycle of saidpulsating'supply potential frequency and circuit means arranged: toconnect said re sistance between the control potential and the controlelectrodes to establish said ion-current potential and to connect saidcapacitance in shunt with said control electrodes to store saidion-current potential.

10. In a relay circuit comprising a pulsating supply potential, acontrol potential variable by external means, a load and a gas dischargetube having at least an anode, a cathode and a grid electrode, said lasttwo elements comprising a pair of control electrodes, and saidsupplypotential being connected through said anode and cathode tosaid load; a,modifying network arranged to connect said control potential and saidcontrol electrodes, including resistance means having sufficientresistance to produce substane tial potential pulses thereacross bypositive ion grid current therethrough, capacitance means, havingsufiicient capacitance to store a substantial portion of saidion-current-produced potential for a time corresponding to at least onehalf. cycle of said pulsating supply potential frequency and circuitmeans arranged to connect said resistance between the control potentialand the control electrodes to produce the ion-current potential, toconnect said capacitance across the control electrodes to store theion-current-produced potential and to apply the algebraic sum of saidion-current-produced potential andsaid control potential. to saidcontrol electrodes.

' ROBERT G. ROWE.

EDWIN F. ZIEMENDORF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,938,742 Demarest Dec. 12, 19332,100,460 Specht Nov. 30, 1937 2,114,828 Bedford Apr. 9, 1938 2,132,264King Oct. 4, 1938 2,190,552 Swart Feb. 13, 1940 2,198,541 Krebs Apr. 23,1940 2,403,609 Perkins July 9,1946 2,404,001 Smith July 16, 19462,420,188 Olving May 6, 1947 FOREIGN PATENTS Number Country Date 443,880Great Britain May 30, 1934 420,100 Great Britain Nov. 26, 1934 OTHERREFERENCES Gleason: Pulse Response, Proc. of the I. R. Feb. 1946..

